Solid polymers of 4-methyl-1-pentene

ABSTRACT

Solid polymers of olefins having at least three carbon atoms per molecule and methods of making such polymers with a chromium-containing catalyst or organometal catalyst system.

This application is a continuation of our copending application Ser. No.648,364 filed June 23, 1967, now abandoned, which is a divisionalapplication of our copending application Ser. No. 558,530 filed Jan. 11,1956, which is a continuation-in-part of applications Ser. No. 333,576filed Jan. 27, 1953, and Ser. No. 476,306 filed Dec. 20, 1954, both nowabandoned.

This invention relates to polymerization. In one aspect it relates tonovel solid polymers having unique and desirable properties.

The production of solid polymers of olefins by the use of aluminumhalide catalysts and by high pressure thermal or peroxide-catalyzedpolymerization is known in the art. In the past, all known solidpolymers of olefins have been considered equivalents of each other.

We have found that olefin polymers produced by certain processes are notequivalent to those produced by the prior art processes set forth above.We have also found that differences between different polymers arecorrelatable with the infrared absorption characteristics of suchpolymer and with X-ray diffraction data.

An object of the invention is to produce a novel polymer. Another objectof the invention is to produce a solid polymer having unique anddesirable properties. Another object is to produce a polymer which isresistant to deformation under the influence of heat. Another object isto produce a crystalline polymer. Another object is to produce acrystalline solid polymer from olefins having at least 3 carbon atomsper molecule. Other objects and advantages of the invention will beapparent to those skilled in the art from an inspection of the followingdisclosure and drawing in which:

FIG. 1 is an infrared absorption spectrum of a polymer according to thisinvention.

FIG. 2 is a similar spectrum for another polymer according to thisinvention.

FIG. 3 is an X-ray diffraction pattern for the polymer, the spectrum ofwhich is shown in FIG. 1.

FIG. 4 is an X-ray diffraction pattern for a polymer, the infraredspectrum of which is shown in FIG. 2.

FIG. 5 is a chart showing the thermal depolymerization curve for variouspolyolefins, including commercial polyisobutylene and several polymersof the invention.

According to this invention, there are provided crystalline, normallysolid polymers of olefins having at least 3 carbon atoms per molecule.The polymers of this invention are further characterized by the regularrecurrence within the molecule of certain atomic groupings, in contrastto more or less random grouping of atom groups within the molecule inprior art polymers. This characteristic is established by X-raydiffraction data. A further characteristic of polymers according to thisinvention is that they have relatively high densities as compared withthe predominantly amorphous polymers produced by the prior art. Anothercharacteristic of the polymers according to this invention is that theyhave relatively high melting points in comparison with prior artamorphous polymers. A further characteristic of polymers according tothis invention is that they are insoluble in ordinary solvents such asmethyl isobutyl ketone, chloroform, carbon tetrachloride, symmetricaldichloroethane, benzene, normal pentane, normal hexane and normalheptane at temperatures up to about the boiling points of these solventsat atmospheric pressure. Thus it will be apparent to those skilled inthe art that the solid polymers of this invention are particularlyuseful where a heat-resistant polymer is desired. The polymers of thisinvention can be utilized for the preparation of molded articles such ascontainers for fluids and particularly containers such as bottles whichare required to be sterilized by contact with steam at temperatures ofthe order of 212° to 230° F. The polymers can be extruded to form pipeand tubing, which can be used for the transfer of hot liquids or can beutilized to transfer liquids through relatively warm surroundingswithout deformation of the conduit. Polymers can also be extruded in theform of filaments which can be woven into textiles or films which areresistant to relatively high temperatures and can be used for packagingfoods, drugs, etc. Films can also be formed from these polymers bymolding or rolling. A further characteristic of polymers of thisinvention is their relative hardness. The value of this characteristicin connection with the uses mentioned above will be immediately clear tothose skilled in the art.

Throughout the specification it is to be understood that the totalpolymer designates all polymer boiling above the monomer (but notincluding the diluent, of course); the semi-solid polymer constitutesthe mixture or residuum remaining after distilling off, or otherwiseremoving, the light oil boiling below about 900° F.; the tacky polymeris the lower molecular weight portion of the semi-solid polymer whichcan be extracted therefrom, e.g. with n-C₅ ; and the solid polymer isthe higher molecular weight portion of the semi-solid fraction, whichconstitutes the raffinate or insoluble portion left from the extractionwith n-C₅ or methylisobutylketone (MIBK).

The polymer produced from alpha olefins over a chromia-containingcatalyst has a wide molecular weight range. The total polymer may beseparated into three fractions, a liquid fraction, a tacky fraction, anda solid fraction containing material at the upper end of the molecularweight range. The separation may be carried out by a number of differentmethods, and the relative amount and the characteristics of the variousfractions will depend somewhat on the method of fractionation used. Twomethods of separation are currently used: (1) The total polymer isfractionated under vacuum to produce an overhead fraction having an endpoint, corrected to atmospheric pressure, of 850° or 900° F. The kettlematerial is then extracted with MIBK at a temperature somewhat aboveroom temperature yielding as extract the tacky polymer and as raffinatethe solid polymer. (2) The total polymer is subjected to extraction withpentane at room temperature, the solid fraction being insoluble. Thepentane-soluble material is then extracted, usually twice, with MIBK atroom temperature yielding an extract of normally liquid oil and araffinate of tacky polymer. Method (1) produces considerably less oiland more tacky polymer than method (2). The oil produced by method (2)probably contains in solution some of the lower molecular weight tackypolymer.

The monomers which are used to produce the polymer according to thisinvention can be defined as olefins having at least 3 carbon atoms permolecule. A preferred class of these materials is defined as 1-olefinshaving at least 3 carbon atoms per molecule, a maximum chain length of 8carbon atoms, and no branching nearer the double bond than the4-position. A preferred class of olefin monomers according to thisinvention is defined as normal 1-olefins and methyl substituted1-olefins having from 3 to 8 carbon atoms per molecule, the methylsubstituent being no nearer the double bond than the 4-position.Examples of specific olefinic monomers are propylene, 1-butene,1-pentane, 1-hexene, 4-methyl-1-pentene and 1-heptene.

The polymers according to this invention can be produced by contacting amonomer of the type above described, under polymerization conditions,with a catalyst comprising chromium oxide associated with at least oneoxide selected from the group consisting of silica, alumina, zirconiaand thoria. In this type of catalyst, chromium oxide is an essentialingredient, and it is much preferred that at least part of the chromiumbe in the hexavalent state. The existence of chromium in the hexavalentstate can be determined by leaching the catalyst with water anddetermining the chromium dissolved in the leachings. The catalyst can beconsidered to be chromium oxide supported on one of the other oxidesaforementioned. It appears however that the non-chromium component isnot a mere inert support, since it appears that the non-chromiumcomponent contributes some of the activity of the composite catalyst.The foregoing characterization of the non-chromium component of thecatalyst includes various mixtures or composites of the individualoxides mentioned. Thus the various compounds or composites known in theart as silica-alumina, silica-zirconia and silica-alumina-zirconia, aswell as similar composites are within the scope of the foregoingcatalyst description. Indeed one of the preferred non-chromiumcomponents of the catalyst is a silica-alumina composite of the typegenerally used as catalyst in the cracking art.

The chromium oxide catalyst can be prepared by impregnation ofparticulate silica, alumina, or silica-alumina, for example, with asolution of chromium oxide or a compound convertible to the oxide bycalcination, followed by drying and activation of the composite at atemperature in the range of 450° to 1500° F. for a period of 3 to 10hours or more. Activation is conducted by heating in a stream of gas. Itis preferred that the gas contain oxygen and be substantiallywater-free. However, inert gases, such as carbon dioxide and nitrogen,can be used. It is found that within this activation range oftemperature treatment of the catalyst, the character of the polymer canbe controlled. When the catalyst is activated at temperatures in theupper part of the range, particularly from 1300° to 1500° F., thepolymers obtained from propylene and heavier olefins have a loweraverage molecular weight and contain less tacky and solid polymer, whileactivation temperatures in the lower part of the range produce acatalyst which effects an increase in molecular weight of the polymerand the production of larger proportions of heavy tacky and solidpolymer. The catalyst can be prepared using, as starting material,chromium trioxide, chromic nitrate, chromic acetate, chromic chloride,chromic sulfate, ammonium chromate, ammonium dichromate, or othersoluble salts of chromium. The highest conversions were obtained fromthe catalyst that contained only chromium oxides after activation.Impregnation with chromium trioxide (CrO₃) is preferred, althoughchromic nitrate can be used with similar results. It is believed thatthe catalyst prepared from the chloride and that prepared from thesulfate are at least partially converted to oxide during activation. Theamount of chromium, as chromium oxide, in the catalyst can range from0.1 to 20 or more weight percent. Chromium contents as high as 50 weightpercent are operative, but amounts above 20 weight percent appear tohave little added advantage. A preferred non-chromium component or"support" is a silica-alumina composite containing a major proportion ofsilica and a minor proportion of alumina. While the method of preparingthe silica-alumina composite undoubtedly affects the catalyst activityto some extent, it appears that silica-alumina composites prepared byany of the prior art processes for preparing such catalytically activecomposites are operative for the process of this invention.Coprecipitation and impregnation are examples of such processes. Onesupport that has been found particularly effective is a coprecipitated90 percent silica-10 percent alumina support. It is found that steamtreatment of this support, i.e., silica-alumina, or silica withoutappreciable alumina, improves the activity and life of the catalystcomposite in a polymerization reaction. A silica support of lowersurface area and larger pore size is a better support than one havingextremely high surface area and small pore size. These factors arebelieved to be of importance in the removal of the heavy polymer fromthe surface of the catalyst composite. A chromium oxide-alumina catalysthas about two-thirds the activity of a chromium oxide-silica-aluminacatalyst. It is necessary for some of the chromium to be in thehexavalent state to act as an active promoter or catalyst for thepolymerization reaction of this invention. It is preferred to usecatalyst in which the amount of hexavalent chromium is at least 0.1percent of the weight of the catalyst composite, as determined byascertaining the water-soluble chromium present by leaching with waterand determining the dissolved chromium in the leachings.

The preferred steam activation of the silica-alumina base of thecatalyst is conducted at a temperature of approximately 1200° F. for 10hours utilizing 5 volume percent steam admixed with 95 volume percentair. In the steam activation treatment, the temperature can be variedfrom 1100° to 1300° F. and the steam content of the steam-air mixturecan range from about 3 to about 10 percent. The time of treatment canvary from about 4 to about 15 hours.

The molecular weight of the product can be changed by pretreating thecatalyst base, preferably before addition of the chromium oxide, with afluoride, alone or in aqueous or non-aqueous solution, e.g., aqueous oranhydrous hydrogen fluoride or other organic or inorganic fluoride,especially a volatile fluoride, and heating, e.g., at from 300° to 1100°F. for from 0.5 to 10 hours, to remove residual fluoride, This treatmentresults in a catalyst which, after addition of the chromium oxide,produces a polymer of increased molecular weight and flexibility. From0.001 to 0.2 part by weight of fluoride per part by weight of oxidetreated produces the improved results.

The terms "support" or "base", as used herein, are not to be narrowlyinterpreted. They are not limited to mere inert components of thecatalyst mass. The non-chromium components appear to impart to thecatalyst at least part of its activity, and variations in their identityand proportions affect the catalyst activity. The "support" ispreferably utilized in porous form, e.g., a gel.

Other methods of preparing the catalyst, e.g., coprecipitation, arewithin the scope of the invention.

The temperature at which the polymerization is conducted is ordinarilywithin the range 100° to 450° F. However, these temperatures are notabsolute limitations. The upper limit is ordinarily that temperature atwhich the hydrocarbon appears to deactivate the catalyst by somereaction other than polymerization, e.g., reduction, or that temperatureat which depolymerization or cracking predominates over polymerizationto the extent that no polymer is ultimately formed. The lowertemperature limit is ordinarily determined by operating conditions suchas viscosity and, in the case of fixed-bed operation, plugging of thecatalyst bed by the deposition of heavy polymer therein. A preferredtemperature range is from about 150° to about 375° F. and a morepreferred range is from about 150° to about 275° F.

The reaction can be conducted in the liquid phase or in the gaseousphase, liquid phase operating ordinarily being preferred. It is oftenadvantageous, particularly when operating in the liquid phase, toutilize a solvent or diluent in admixture with the olefin feed. Thisdiluent should be one which can be maintained in the liquid phase underthe reaction conditions and one which will not deleteriously affect thecatalyst.

The pressure is preferably high enough to maintain the diluent in theliquid phase and to assure that olefins not liquefied under theseconditions are dissolved in the liquid phase in sufficient amount. Thisoften, but not invariably, requires a pressure of at least 100 to 300psi, depending on the feed and the temperature, and a pressure ofapproximately 500 psi is to be preferred. The pressure can be as high as700 psi or higher, if desired. It can be as low as atomspheric when, forexample, the reaction is conducted in the gaseous phase. As a generalrule, high pressures favor the production of high molecular weightpolymers, all other conditions being constant. The feed rate can rangefrom 0.1 to 20 liquid hourly space velocity with a preferred range of 1to 6 liquid hourly space velocity in a liquid-phase process withfixed-bed catalyst. Hydrocarbon diluents, preferably paraffins and/orcycloparaffins, serve as solvents for the polymer products to aid in theremoval of the product from the catalyst in the reactor. The diluentsinclude aliphatic paraffins having from 3 to 12, preferably 5 to 12,carbon atoms per molecule. Any of the paraffins which is a solvent forthe heavier polymer at temperatures in the operating range is suitable.Any hydrocarbon diluent which is relatively inert, non-deleterious, andliquid under the reaction conditions of the process can be utilized.Diluents that have been used successfully include propane, iso-butane,normal pentane, isopentane, isooctane (2,2,4-trimethylpentane),cyclohexane, and methylcyclohexane. The heavier paraffinic diluents gavebetter results than the lighter ones, probably because they are bettersolvents for the heavy polymer. Aromatic diluents are, in general, notused, since they appear to decrease the activity of the catalyst. Theyare, however, operative, where short catalyst life can be tolerated.

The polymerization can be effected with a fixed-bed catalyst or with amobile catalyst. A frequently preferred method of conducting thepolymerization reaction comprises contacting the feed olefin with aslurry of the comminuted chromium oxide catalyst in suspension in thesolvent or diluent. The catalyst can be maintained in suspension by amechanical agitation device and/or by virtue of the velocity of theincoming feed olefin. In this type of operation, a large portion of theproduct polymer remains associated with the catalyst, which is withdrawnfrom the reaction zone, as a slurry. The polymer is recovered bydissolution in a solvent of the type described, usually with the aid ofheat and agitation, and the stripped catalyst is recycled and/orregenerated. The regeneration is accomplished by oxidizing the residualcarbonaceous deposit with a controlled concentration of oxygen in aninert gas by conventional procedures. In order to remove polymercompletely from the catalyst, a solvent other than that used as thediluent in the polymerization step can be utilized. Regardless of whichsolvent is used, it is ordinarily desirable to remove adhering solventfrom the catalyst prior to any regeneration step. This can be done bystripping with an inert gas such as nitrogen or steam at a moderatelyelevated temperature.

One of the problems encountered in fixed-bed operation of thepolymerization process of the invention lies in the plugging of thecatalyst with heavy polymer. Periodically reversing the direction offlow of feed through the catalyst bed aids in distributing the heavypolymer over the catalyst and extends the time in which the catalyst canbe utilized before regeneration is required. Effecting the process bycountercurrently contacting a slowly gravitating bed of the catalystwith the liquid feed makes it possible to utilize the catalyst overlonger periods of time before regeneration is necessary and entirelyprevents plugging of the catalyst bed which eventually occurs infixed-bed operation. The olefin-containing feed, together with ahydrocarbon solvent, such as n-pentane or isooctane, under sufficientpressure to maintain liquid phase, is charged into the bottom of thereactor and moved upwardly at a linear velocity which can be sufficientto give some expansion of the bed to prevent plugging by high polymeraccumulation but insufficient to cause substantial top-to-bottom mixingof the catalyst. In this type of operation, it is possible to maintain atop bed temperature in the range of 100° to 150° F. and a bottom bedtemperature in the same range, while the temperature of the middlesection of the bed is maintained in the range of about 200° to 250° F.in propylene or higher 1-olefin polymerization. This type of operationand temperature control effects the production of a larger proportion ofhigh molecular weight polymer in both the top and bottom sections of thebed and increases the yield of tacky and solid polymer. Temperature iscontrolled by regulating the temperature of the feed and the temperatureof the incoming catalyst. The feed cools the hotter catalyst coming fromthe middle or intermediate section of the bed and the cooler catalystadmitted to the top section of the bed cools the liquid passing into thetop section of the bed from the hotter intermediate section. In themoving-bed process, the liquid feed rate is maintained in the range of 2to 6 v/v/hr, the olefin concentration, in the hydrocarbon feed, in therange of 0.1 to 25 weight percent, and the catalyst rate in the range of0.1 to 0.5 v/v/hr. In this process, fresh olefin-containing feedcontacts the less active catalyst at a minimum temperature so thatexcessive reaction is avoided and heavier polymer is produced. Theup-flowing feed is heated by direct heat exchange with hot catalyst fromthe higher temperature region produced by heat of reaction, and thetemperature reaches a maximum at or near the middle of the bed. As thefeed moves on up through the top part of the bed, it becomes moredepleted in olefins and is cooled by direct heat exchange with coolerfresh catalyst. In the top part of the bed, the fresh, highly activecatalyst contacts the olefin-depleted feed at or near the minimumtemperature of the range so that excessive reaction is avoided andheavier polymer is produced. The effluent from the top of the reactorcontains the total polymer (except polymer deposited on the catalyst),together with the hydrocarbon solvent, such as pentane or isooctane.Polymer remaining on the catalyst can be recovered, at least in part, bytreatment of the catalyst with a suitable solvent, such as thosepreviously described herein, at a temperature above reactiontemperature, or by stripping the catalyst with an inert gas at a stillhigher temperature, e.g., 700° to as high as 1100° F. or higher, theeffluent stripping gas being cooled to condense polymer removed therein.The polymer can be recovered from solution in the solvent by evaporationof the solvent. Operation with the temperature gradients indicatedresults in considerable reaction at lower temperatures than wouldotherwise be possible, and ultimately results in the production ofheavier polymer. In addition, excessive reaction in a narrow zone withplugging difficulties and catalyst disintegration are avoided.

Used catalyst can be regenerated in auxiliary equipment in the usualmanner. The catalyst is first washed with a hydrocarbon solvent, such aspentane or isooctane at a temperature in the range of 300° to 400° F.under sufficient pressure to maintain the solvent in the liquid phase.Following this, any remaining solid polymer is removed from the catalystwith dry air diluted with inert gas. The temperature at which the solidpolymer is burned off the catalyst is maintained preferably in the rangeof 900° to 1100° F. Solid polymer is recovered from the solvent used inthe washing step and the polymer-free solvent is reusable in subsequentwashings.

As previously indicated, a preferred method of conducting the reactionis to maintain the catalyst, ordinarily in the form of a powder having aparticle size in the range 20 to 100 mesh, in the form of a suspensionin the diluent or solvent, and passing the monomer through this mixture.The suspension can be maintained by means of a mechanical stirrer and/orby means of the stirring action of incoming monomer. In this type ofoperation, a reaction time or residence time of the reaction mixture inthe reaction zone can range from 5 or 10 minutes to 10 or more hours.Highly satisfactory results are obtained with a residence time in therange 30 minutes to 4 hours.

The total polymer is ordinarily recovered from the hydrocarbon effluentfrom the reactor by evaporation or vaporization of the solvent ordiluent. However, the polymer can also be recovered by cooling the totaleffluent and precipitating the polymer therefrom as an insolubleprecipitate. When a suspended catalyst is used, it is often desirable toremove the catalyst prior to the recovery of the polymer from thesolvent. This can be effected by heating under pressure to dissolve amaximum amount of the polymer and subsequently removing the catalyst bythe use of a filter or a centrifuge or equivalent equipment. However, inmany cases only a few percent by weight of catalyst based on polymerproduced is required, and in many cases less than one weight percent ofthe catalyst based on the weight of the polymer is utilized. Thereforein many cases, it is unnecessary to remove the catalyst from the productpolymer. This is particularly true when the polymer is to be used forthe production of such materials as pipes which are to be embedded inthe earth or in various structures. The particular polymer according tothis invention can be isolated or purified by extracting the totalpolymer with a solvent such as normal pentane, normal heptane or methylisobutyl ketone to remove the more soluble portions. This extraction isordinarily conducted at or a few degrees below the boiling point,ordinarily within 10 or 20 degrees Fahrenheit of the boiling point. Theextract is decanted or otherwise removed and the remaining insolublepolymer can be heated, e.g., in vacuum to remove any adhering solvent.

Another method for producing polymers according to this invention is toutilize as catalyst a metallo organic compound such as an aluminumalkyl, or an aluminum alkyl halide in admixture with certain compoundsof titanium, chromium or molybdenum or similar metals in the same oradjacent groups of the periodic table. An example of a catalyst of thistype is a mixture of triethylaluminum with titanium tetrachloride. Thegeneral conditions of operation are similar to those previouslydescribed. An additional step in the procedure is that the effluent fromthe reactor is ordinarily treated with a compound such as a low boilingketone or alcohol, e.g. methanol, to deactivate the catalyst. Ordinarilythe catalyst residue is allowed to remain in the polymer which isproduced. The reaction is ordinarily conducted in a reactor providedwith a stirrer and is not ordinarily conducted by the fixed-bedtechnique.

The solid crystalline polypropylenes produced according to thisinvention have melting points in the range 230° to 320° F., densities inthe range 0.90 to 0.96, intrinsic viscosities in the range 0.2 to 5.0,and weight average molecular weights in the range 900 to 50,000 andhigher. The intrinsic viscosity is ordinarily determined by the use of asolution of 0.2 gram of the polymer in 50 cc of tetralin at 130° C. Theweight average molecular weight is computed by multiplying thisviscosity by 24,500. This type of molecular weight determination isdescribed by Kemp and Peters, Ind. Eng. Chem. 35, 1108 (1943) and byDienes and Klemm, J. Applied Phys. 17. 458 (June. 1946).

We have produced crystalline polymers of 4-methyl-1-pentene which havemelting points in the range 390° to 425° F.

EXAMPLE I

Individual olefins and diolefins were polymerized in flow type runs overa fixed bed of 3 percent chromium as oxide in chromia-silica-aluminacatalyst at about 600 pounds per square inch at a temperature of about190° F. and two liquid hourly space velocity of feed containing 20 molpercent reactant and 80 mol percent isobutane. Most runs were for 4 to 6hours. The results of the conversions and the qualitative nature of thepolymers are given in Table I.

                  TABLE I                                                         ______________________________________                                                    Average                                                                       Conversion,                                                       Monomer     %          Type of Polymer, etc.                                  ______________________________________                                        propylene   91         tacky, semi-solid                                      1-butene    75         tacky, elastic semi-solid                              1-pentene   82         tackier than polypropylene;                                                   semi-solid                                             1-hexene    40-55      very tacky, transparent gel                            4-methyl-1-pentene                                                                        80         solid; tough, not tacky                                ______________________________________                                    

The results show that 1-olefins give the high polymer. Normal 1-olefinsthrough 1-hexene give high polymers which vary in degree of solidity andtackiness as noted.

For the branched 1-olefins tested, any branching closer to the doublebond than the 4-position prevented formation of heavy polymer.4-Methyl-1-pentene gave tough, solid polymer which, however, wassuccessfully expelled from the reactor in continuous-flow operation.

EXAMPLE II

The catalyst used to produce the polymer was prepared by using as a basea silica-alumina coprecipitated composite gel containing 90 weightpercent silica and 10 weight percent alumina. The gel had been treatedwith a mixture of steam and air at an elevated temperature for severalhours prior to use. The gel, in the form of 14 to 28 mesh particles wasimpregnated with aqueous solution of chromium trinitrate nonahydrate(0.78 molar) dried and heated in dry air for about 5 hours at about 950°F. The final catalyst contained about 2 weight percent chromium asoxide, most of which was in the hexavalent state. 57.5 grams of thiscatalyst was charged to a reactor to form a fixed-bed of catalyst 16.5inches deep and 3/4 inch in diameter. A feed mixture comprising 9.12weight percent propylene, 8.19 weight percent propane and 82.69 weightpercent isopentane was passed through the catalyst bed at a temperatureof 190° F., a pressure of 600 psig and a liquid hourly space velocity of2. Total polymer was recovered from the effluent by vaporization of theisopentane and lighter materials. The duration of the run wasapproximately 5 hours. The total polymer was extracted first withchloroform and then with benzene, at a temperature slightly below theboiling point of each solvent, and the insoluble fraction was freed ofadhering solvent by heating in vacuum.

The infrared absorption spectrum of this insoluble polymer is shown inFIG. 1, which is a plot of wave length of the infrared radiation againstpercent of transmission of light through the sample. The markedabsorption at wave lengths of 3.4 and 6.8 microns are characteristic ofall hydrocarbons and indicates the presence of C--H bonds. The markedabsorption band at about 7.3 microns is characteristic of methyl groups.It will further be noted that there is marked absorption of infraredradiation at wave lengths of between 8.5 to 8.6 microns, between 10.0and 10.1 microns, at approximately 10.3 microns, and approximately 11.9microns. These marked absorption bands, especially those at about 8.6,about 10.0 and about 11.9 are characteristic of polymers of thisinvention and, to our knowledge, are not shown by other polymersproduced prior to our production of the polymers herein described. Itwill be further noted that less marked, though definite, absorptionbands appear at about 7.7, about 7.9 to 8.0, about 9.1, about 9.6, about10.6 to 10.7 and at about 11.1 microns. These are also distinguishingcharacteristics of polymers according to this invention.

From FIG. 1 it will be noted that the transmission minima are quitesharp, i.e., the slope of the curve on each side of the minima is quitesteep. This phenomenon of sharp, V-shaped minima in the transmissioncurves shows that the material examined was highly crystalline, i.e. inexcess of 80 percent crystallinity. Marked crystallinity is also shownby X-ray scattering curves of this polymer shown in FIG. 3. The X-rayscattering data also indicate the existence of regularly recurringgroups of atoms within the molecule. Propylene polymer of this type hasa melting point of the order of 290° to 305° F. In most cases, themelting point is at least 280° F.

Data in this example show that polymers according to this invention arehighly crystalline and have infrared absorption characteristics whichare characteristic of these and, to our knowledge, no other polymers.

EXAMPLE III

Propylene was polymerized in substantially the same manner as describedin Example I except that the catalyst was prepared from silica-aluminahaving a particle size from 8 to 14 mesh, the final catalyst containing4 weight percent chromium and the activation was conducted by heating indry air at 730° F. Furthermore, the polymerization was conducted at 190°F. and 500 psig. The duration of this run was approximately 38 hours.Five and one-half pounds of total polymer was produced. A 2-inchdiameter reactor was used.

The polymer was fractionated by extraction with methylisobutyl ketone. Afirst fraction was obtained which was insoluble in methylisobutyl ketoneat 200° F. This fraction amounted to 5 percent of the total polymer. Asecond fraction which was insoluble in methylisobutyl ketone at 160° F.but soluble at 200° F. amounted to 7 percent of the total polymer. Athird fraction which was insoluble in methylisobutyl ketone at 120° F.and soluble at 160° F. amounted to 12 percent of the total polymer. Afurther fraction of the polymer was obtained by treating the originaltotal polymer with normal heptane at 120° F., recovering theheptane-insoluble fraction, dissolving this fraction in benzene, andreprecipitating by the addition of methyl alcohol. The fraction thusrecovered was an extremely hard solid. This fraction and the threefractions previously described were analyzed by infrared spectralanalysis and found to have spectra closely similar to that shown in FIG.1.

1-Butene and 4-methyl-1-pentene can be polymerized in substantially thesame manner as previously described and produce crystalline polymers.One sample of 4-methyl-1-pentene polymer thus obtained had a meltingpoint of 394° to 421° F. A second similar polymer of 4-methyl-1-penteneproduced in the same general manner had a melting point of 410° to 420°F.

EXAMPLE IV

The catalyst of the type described in Example I was suspended incyclohexane in a reactor provided with a motor-driven stirrer. Gaseouspropylene was continuously pressured into the reactor to maintain apressure from 80 to 340 psig. The temperature of polymerization was 180°F. and the duration of the run was 6 hours. The total amount of catalystused was 10.2 grams and a yield of 9.3 grams of polymer per gram ofcatalyst was obtained. The fraction of the total polymer which wasinsoluble in cyclohexane at approximately 90° F. amounted toapproximately 15.3 weight percent of the total polymer. This fractionhad a density, at 25° C., of 0.936%. This fraction had an infraredabsorption spectrum closely similar to that in FIG. 1.

EXAMPLE V

Propylene was polymerized in a one-gallon stainless steel autoclaveprovided with a mechanical stirrer and heat-exchange coils. Thefollowing materials were charged to the clean, dry reactor whilemaintaining an atmosphere of prepurified nitrogen.

Cyclohexane: 2 liters

Triethylaluminum: 5 milliliters

Titanium tetrachloride: 2 milliliters

With the reactor and contents at a temperature of 95° F., propylene wasgradually charged to the reactor. After 5 minutes, the temperature hadincreased from 95° to 104° F. and the pressure was recorded as 30 psig.At the end of an additional 17 minutes the temperature had increased to105° F. and the pressure had increased to 60 psig. The temperature andpressure increased gradually and at the end of an additional period of 3hours and 8 minutes, the temperature was 162° F. and the pressure was140 psig. During this period 2.51 pounds of propylene had been chargedto the reactor. At this point the charging of propylene was terminatedand the reactor and contents were allowed to cool gradually. After onehour and 40 minutes the temperature had decreased to 132° F. and thepressure had decreased to 50 psig. The reaction mixture was then cooledby passing tap water through the heat exchange coils and finally theexcess propylene was bled off.

Isopropyl alcohol was added to the reaction mixture to precipitate thepolymer. The solid product was washed with additional isopropyl alcoholand finally with methyl alcohol. Polymer was dried in a vacuum oven forapproximately 24 hours.

This material was combined with propylene polymer obtained from twoadditional runs carried out under similar conditions in which a mixtureof triethylaluminum and titanium tetrachloride had been employed as thecatalyst.

The combined polypropylene (approximately 915 grams) was extracted forapproximately one-half hour with 4 liters of normal heptane maintainedat its boiling point. This extraction was repeated three additionaltimes using 4 liters of normal heptane for each extraction. Theinsoluble propylene polymer was dried for 60 hours in a vacuum oven andapproximately 152 grams of dry polypropylene was obtained. The solubleportion was recovered by pouring the normal heptane solution intoisopropyl alcohol and drying the precipitated material. About 417 gramsof polypropylene which was soluble in normal heptane under theconditions of extraction was obtained.

The insoluble polypropylene had the following physical properties:

    ______________________________________                                        Density, grams per cc at room temp.                                                                  0.905                                                  Melt index             0.341                                                  Molecular weight (based on melt index)                                                               46,600                                                 Inherent viscosity     3.360                                                  Molecular weight (based on inherent                                           viscosity)             82,175                                                 Melting point, °F.                                                                            300                                                    Ash content, %         0.254                                                  Flexibility            Good                                                   No strength temperature °F.*                                                                  318                                                    ______________________________________                                         *Determined by suspending a 27.5 gm. weight by a standard tensile specime     of the polymer and raising the temperature 5° F./min until the         weight drops 1 inch.                                                     

The total sample of polypropylene (prior to fractionation) had a meltingpoint of 252°±3° F.

The titanium tetrachloride was obtained from Fisher Scientific Co.

The propylene used was Phillips Petroleum Co. pure grade (99 mol percentpropylene).

The cyclohexane was Phillips Petroleum Co. commercial grade containingapproximately 85 mol percent cyclohexane and this material had beenthoroughly dried prior to use.

The triethylaluminum was prepared according to the following generalprocedure. First, ethyl chloride was reacted with metallic aluminum atapproximately 248° to 302° F. to form a mixture of ethylaluminumdichloride and diethylaluminum chloride. This mixture was distilled andthe distillate was found to contain 52.7 weight percent chlorine. Themixture was treated in a second step with magnesium and ethyl chlorideat about 230° to 248° F. for 6 hours, and for an additional 3-hourperiod at about 356° F. Thus a major portion of the ethylaluminumdichloride present in the reaction mixture from the first step wasconverted to diethylaluminum chloride. The reaction mixture from thissecond step was distilled and the distillate was found to contain 33weight percent chlorine. (The theoretical for diethylaluminum chlorideis 29.4 percent chlorine). The distillate from the second step wastreated with sodium in cetane for 45 minutes at 248° F. and for anadditional 4 hours at 320°-356° F. The product was distilled and wasfound to be substantially pure triethylaluminum. Analysis indicated itcontained 0.51 percent chlorine.

A sample of the insoluble fraction of the polypropylene preparedaccording to this example was investigated by infrared spectral scanningand by X-ray diffraction. The infrared spectrum is shown in FIG. 2 andit is readily seen that this spectrum is quite similar to that shown inFIG. 1.

Similar results are obtained when the catalyst is a mixture of titaniumtetrachloride and lithium aluminum hydride.

The X-ray diffraction pattern of the above-described insoluble fractionis shown in FIG. 4. This X-ray diffraction pattern, as well as that inFIG. 2, which is similar, indicates a highly crystalline structure, asshown by the definite peaks of intensity of the diffracted X-rays.

The infrared absorption spectra previously described were obtainedutilizing a Perkin-Elmer Model 21 spectrophotometer. The samples ofpolymer used were 60 microns in thickness.

Unless otherwise defined, the term "molecular weight" as used hereinmeans molecular weight as determined by viscosity measurement in themanner previously set forth herein.

The X-ray diffraction patterns were determined with a diffractometerutilizing copper K.sub.α radiation and a Geiger counter.

EXAMPLE VI

The data presented in FIG. 5 were obtained by placing a sample of thepolymer to be tested in a bomb and heating slowly. Pressure andtemperature were measured at intervals. The polymers were all maintainedat each temperature for comparable times before the pressure was read.

FIG. 5 qualitatively compares the stabilities of long chain polyolefinsprepared in accordance with the invention over chromia-silica-aluminacatalyst with that of the polyisobutylene recovered from commercial VIimprover. It will be seen from the figure that the commercialpolyisobutylene is considerably less stable than are the polyolefins ofthe subject invention. Whereas the former began to decompose at about600° F., the latter (polymers of propylene, 1-butene, 1-pentene,1-hexene, and 4-methyl-1-pentene) began to decompose at about 700°-725°F. A 1:1 copolymer of 1-hexene and 4-methyl-1-pentene, prepared overchromia-silica-alumina catalyst, exhibited about the same stability asthe polymer of 4-methyl-1-pentene.

EXAMPLE VII

A 1-hexene polymer was prepared at 215° F. over chromia-silica-aluminacatalyst. The polymer was concentrated by extraction withmethylethylketone. The polymer was dissolved completely in MEK at 80° C.Upon cooling to room temperature, a solid phase, which amounted to 47.5weight percent of the original polymer, was recovered by decantation.The solid material was again treated with MEK at 80° C., partialsolution being obtained, after which the mixture was cooled to roomtemperature and decanted. The remaining polymer amounted to 32.2 weightpercent of the original polymer.

EXAMPLE VIII

Another modification is a combination process comprising the steps ofpolymerizing propylene over nickel oxide-silica-alumina catalyst toproduce a dimer containing 4-methyl-1-pentene, 4-methyl-2-pentene,2-methyl-2-pentene and 1-, 2- and 3-hexene; fractionating this mixtureto produce fractions of (1) 4-methyl-1-pentene, (2) 4-methyl-2-pentene,(3) 1-hexene and (4) 2- and 3-hexene; isomerizing separately the4-methyl-2-pentene and the 2- and 3-hexenes to the 1-isomers; combiningthese 1-isomers with 1-isomers originally produced, and polymerizingseparately or copolymerizing these 1-isomers (1-hexene and4-methyl-1-pentene) over chromia-alumina-silica catalyst. The 1-hexenepolymer is a tacky transparent gel suitable for a viscosity-indeximprover. The 4-methyl-1-pentene polymer is a tough solid polymersuitable for a substitute for natural waxes.

While certain compositions, examples and process steps have been givenfor purposes of illustration, it is clear that the invention is notlimited thereto. It is also clear that we have provided uniquecrystalline solid polymers of olefins having more than 2 carbon atomsper molecule.

These polymers are characterized by constantly recurring atomicgroupings in which the substituent groups (e.g. methyl and other sidegroups or chains) are oriented in the same general direction.

We claim:
 1. A normally solid homopolymer of 4-methyl-1-pentene.
 2. Apolymer of claim 1 having a melting point in the range of 390° to 425°F.
 3. A normally solid crystalline homopolymer of 4-methyl-1-pentene. 4.The polymer of claim 3 having a melting point in the range of 390° F. to425° F.
 5. The homopolymer of 4-methyl-1-pentene according to claim 4characterized by a melting point of 394° to 421° F.
 6. The homopolymerof 4-methyl-1-pentene according to claim 4 characterized by a meltingpoint of 410° to 420° F.
 7. Filaments, suitable for textiles, of atough, crystalline homopolymer of 4-methyl-1-pentene.
 8. Films, suitablefor packaging, of a tough, crystalline homopolymer of4-methyl-1-pentene.
 9. A tough solid crystalline homopolymer of4-methyl-1-pentene characterized as insoluble in methylisobutyl ketone,chloroform, carbon tetrachloride, symmetrical dichloroethane, benzene,n-pentane, n-hexane, and n-heptane, at temperatures up to the boilingpoint of these solvents at atmospheric pressure.
 10. A normally solidcrystalline homopolymer of 4-methyl-1-pentene prepared by contacting4-methyl-1-pentene monomer under polymerization conditions with acatalyst comprising chromium oxide associated with at least one oxideselected from the group consisting of silica, alumina, zirconia, thoria,and composites wherein at least some of the chromium of some chromiumoxide is in the hexavalent state.
 11. The homopolymer according to claim10 wherein said catalyst contains an amount of chromium, as chromiumoxide, in the range of 0.1 to 20 weight percent.
 12. A normally solidtough crystalline homopolymer of 4-methyl-1-pentene prepared bycontacting 4-methyl-1-pentene monomer under polymerization conditionswith a catalyst comprising chromium oxide associated with at least oneoxide selected from the group consisting of silica, alumina, zirconia,and thoria, or a composite, wherein said chromium oxide catalyst isprepared by impregnation of one of said oxides with a solution ofchromium oxide or a compound convertible to the oxide by calcination,followed by drying and activation of the resulting catalyst composite ata temperature in the range of 450° to 1500° F. for an effective time,wherein the amount of chromium, as chromium oxide, in the resultingactivated catalyst ranges from about 0.1 to 20 weight percent, whereinat least some of the chromium in said chromium oxide is in thehexavalent state.
 13. The process of preparing a homopolymer of4-methyl-1-pentene which comprises the steps of:(a) dimerizing propyleneover nickel oxide-silica-alumina catalyst to produce a dimer admixturecontaining 4-methyl-1-pentene, 4-methyl-2-pentene, 2-methyl-2-pentene,and 1-,2-, and 3-hexene, (b) fractionating said admixture to producefractions of (1) 4-methyl-1-pentene, (2) 4-methyl-2-pentene, (3)1-hexane, and (4) 2- and 3-hexene, (c) isomerizing the4-methyl-2-pentene to further 4-methyl-1-pentene, and (d) polymerizingthe fraction of 4-methyl-1-pentene and the further 4-methyl-1-pentene to4-methyl-1-pentene crystalline homopolymer under polymerizationconditions employing a catalyst of a chromium oxide supported on atleast one oxide of silica, alumina, zirconia, and thoria, wherein atleast some of said chromium and said chromium oxide is in the hexavalentstate.